In recent years, a demand for a bandwidth guaranteed service that guarantees a user's communication quality is increasing. When the bandwidth guaranteed service is a service that when a user requests communication whose bandwidth is guaranteed to a network, the network side secures a required bandwidth of the user, and the network that guarantees the user's required bandwidth is provided to the user.
As a trunk-line data service network for providing the bandwidth guaranteed service, conventionally, the IP/MPLS (Internet Protocol/Multi-Protocol Label Switching) network has spread widely. In the IP/MPLS network, a packet is transferred not by the related art IP routing but by label switching, and an end-to-end logical communication path (logical path) whose bandwidth is guaranteed for every session by a decentralized control between communication nodes that form the network.
On the other hand, communication enterprises that provide the bandwidth guaranteed service with the transmission networks using a centralized-control-type communications protocol are increasing in number. The centralized-control-type communications protocols are communications protocols, such as MPLS-TP (Multiprotocol Label Switching-Transport Profile), for example.
The transmission network can provide the logical path excellent in confidentiality as compared with a related art IP/MPLS network, and features that an OAM (Operation Administration and Maintenance) function of monitoring failures in the communication route and a QoS (Quality of Service) function of guaranteeing a quality of service are strengthened. In order to attain higher advancement of the present IP service using features of these transmission networks, there is started an examination of a scheme in which the related art IP/MPLS network (communication network) is connected to a user side and an IP inter-work technology of connecting the transmission network to the core side is achieved by standardization of IETF (Internet Engineering Task Force) etc. Incidentally, a reason why the related art IP/MPLS network is used for the user side is to aim at reduction of the cost.
In order to realize an IP inter-work described above, it is necessary to select a centralized control that is a network control method adopted in the transmission network or the decentralized control that is a network control method adopted in the IP/MPLS network, and to connect the transmission network and the IP/MPLS network.
Here, the both network control methods will be compared. The centralized control is a method whereby a managing server controls the network. For this reason, although a load tends to concentrate on the managing server in the centralized control and flexibility of a network design is inferior to the decentralized control, since the managing server can grasp the whole state of the network, ease of management, such as cut-off of the communication route in which a failure occurs and setting of an optimal route, is superior to the decentralized control. On the other hand, since in the decentralized control, each communication node that forms the IP/MPLS network controls the network autonomously, the decentralized control is superior to the centralized control in the flexibility and expandability of the network design, but it is difficult to optimize route setting and clarify a position of the failure and an influence of the failure because each communication node cannot grasp the whole state of the network.
From the viewpoint of advancement of an IP service, it is desirable that the IP inter-work is realized by the centralized control.
Moreover, a method for constructing the logical path of the transmission network and the IP/MPLS network will be explained. Generally, the logical path of the transmission network is constructed by an administrator statically setting up a route and a guaranteed bandwidth of the logical path. On the other hand, a logical path of the IP/MPLS network is constructed by each communication node that forms the IP/MPLS network dynamically setting up a route based on network parameters (link cost, the number of hops, etc.). Moreover, when the bandwidth guaranteed service is provided in the IP/MPLS network, each communication node constructs the logical path using a dynamic bandwidth reservation protocol, such as RSVP-TE (Resource Reservation Protocol-Traffic Engineering).
FIG. 15 is an explanatory drawing of an outline of a bandwidth prediction processing of the IP/MPLS network using the RSVP-TE.
First, when a transmitting host 6 requires provisioning of the bandwidth guaranteed service to a communication node 1 that is connected to itself, the communication node 1 transmits a path message 4 to a communication node 3 to which a receiving host 7 is connected along a communication route being dynamically determined. The path message 4 contains a session ID (S-ID), a user class (Class) that is a value showing a user's priority, and the required bandwidth (BW).
When an available bandwidth of a link connected with the communication node of a next hop can present the required bandwidth contained in the path message 4, each of the communication nodes 1 and 2 transmits the path message 4 to the communication node of the next hop.
When receiving the path message 4, the communication node 3 to which the receiving host 7 is connected transmits a resource reservation message 5 to the communication node 1. The resource reservation message 5 contains the session ID (S-ID), the ID (IP-ID) of the logical path that is constructed, and the required bandwidth (BW).
This enables each of the communication nodes 1 to 3 to construct the logical path of End-to-End, while setting up reservation of the required bandwidth. As described above, in order to realize the IP inter-work, a technology of providing the bandwidth guaranteed service by connecting the logical path of the transmission network constructed by the centralized control to the logical path of the IP/MPLS network dynamically constructed by the decentralized control is required.
As a related method for providing the bandwidth guaranteed service, there is known a method for securing the user's required bandwidth by dynamically constructing the logical path by the centralized control in the IP/MPLS network (e.g., refer to Japanese Unexamined Patent Application Publication No. 2005-217838). Specifically, the managing server constructs all the logical paths in the IP/MPLS network by the centralized control and distributes traffic in the IP/MPLS network by changing the logical path based on a usage status of resources.
Moreover, a method for providing the bandwidth guaranteed service in an ATM (Asynchronous Transfer Mode) network is known (e.g., refer to Japanese Unexamined Patent Application Publication No. Hei11(1999)-136256). Specifically, in an ATM network where a PVC (Permanent Virtual Connections) system in which the administrator statically constructs the logical path and an SVC (Switched Virtual Connections) system in which the logical path is dynamically constructed between the nodes are intermingled, in order to restrict a bandwidth that an SVC session uses, a threshold is set to a total value of the bandwidths of the logical paths constructed in the SVC system. This makes the total value of the bandwidths used by the SVC sessions become less than or equal to the threshold, which enables the bandwidth of the SVC session using static logical paths to be secured. Moreover, when the available bandwidth for newly connecting a PVC session runs short, establishment of the PVC session is prioritized by changing a threshold of the SVC session to a lower value, and making a new session may not be received until a guaranteed bandwidth of the SVC session becomes lower than the threshold after the change.